This application claims the benefit of Korean Application No. 2001-68819, filed Nov. 6, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to a hard disk drive comprising a flexible printed circuit to minimize vibration energy of noise.
2. Description of the Related Art
A hard disk drive is an auxiliary memory device of a computer to write and read information on a magnetic disk by using a magnetic head.
FIG. 1 illustrates the structure of a conventional hard disk drive 20. Referring to FIG. 1, the conventional hard disk drive includes a disk 13 to store information, a spindle motor 15 to rotate the disk 13, an actuator 23 having a magnetic head 25 to write and reproduce information on and from the disk 13, a voice coil motor 21 to drive the actuator 23, a flexible printed circuit (FPC) 11 to transfer an electric signal from a printed circuit board (PCB) (not shown) to the actuator 23, and a bracket 31 to support the FPC 11.
The disk 13 is formed of a parking zone micro-processed by a laser at an inner region of the disk 13 and a data zone at the outer circumference of the parking zone to write magnetic signals. The disk 13 is coupled with the spindle motor 15 to mount the magnetic head 25 in a power-off state. Servo signals to report the location of information to be written are pre-written on tens of thousands of concentric tracks on the disk 13.
The actuator 23 includes a fantail unit 19 having the voice coil motor 21 to drive the actuator 23, a pivot bearing 17 as a rotating center for the actuator 23, and the magnetic head 25 having a write head to write data on the disk 13 and a read head to reproduce information from the disk 13.
The PCB transfers electric signals to the FPC 11 so the FPC 11 can transfer the electric signals to the actuator 23. The electric signals are transferred from the actuator 23 to the voice coil motor 21. The actuator 23 is rotated centering upon the pivot bearing 17 by electromagnetic force from interaction between electric current and magnets in the voice coil motor 21. Accordingly, the actuator 23 moves from the parking zone to the data zone.
FIG. 2 illustrates the structure of the conventional FPC 11. Referring to FIG. 2, head signal patterns (RDX; Read Data X, RDY; Read Data Y, WDX; Write Data X, WDY; Write Data Y) to transfer and/or receive the electric signals to and from the magnetic head through a pre-amplifier (not shown), voltage patterns (VDD; positive DC supply and VSS; negative DC supply) to supply voltage to the pre-amplifier, a ground (GND) to ground, and a current pattern (VC; Voice coil) to apply current to the voice coil motor 21, are arranged on the conventional FPC 11.
In the case of writing and/or reading data in the hard disk drive 20, the magnetic head 25 is positioned above the tracks of the rotating disk 13 to write and/or read data. It is most preferable that the track of the rotating disk 13 forms an exact circle, and the magnetic head 25 precisely writes and reads data. However, in reality, the disk 13 rotates in a distorted circular shape caused by vibration of the spindle motor 15. Accordingly, displacement between the track and the magnetic head, known as runout, occurs.
Two kinds of runout include repeatable runout (RRO), which repeats every rotation and non-repeatable runout (NRRO), which does not repeat every rotation.
In RRO, the rotation of the disk 13 forms a waveform with a specific period caused by the assembly deflection of the disk 13 or vibration of the hard disk drive 20. Since the waveform is periodical, location difference between the track and the magnetic head 25 can be compensated for by recording waveform information in a servo.
In order to compensate for RRO and test reliability, a burn-in test is performed in a process of manufacturing the hard disk drive by varying conditions such as temperature and voltage. However, it is difficult to completely compensate for RRO because the effects of various factors like FPC bias, windage bias, and heat, in the manufacturing process, are complicated. The FPC bias means the force applied from the FPC to a head stack assembly (HSA). The windage bias means the force applied to the HSA according to the effect from rotating fluctuation of the disk to the FPC.
In the FPC 11, since the head signal patterns RDX, RDY, WDX, and WDY are physically close to the current pattern VC and the voltage patterns VDD and VSS through which a relatively large current flows, noise affects the head signal patterns RDX, RDY, WDX, and WDY. In addition, a low frequency of about 340 Hz caused by the characteristic frequency of the FPC 11 affects a servo control.
Especially, since the write head signal patterns WDX and WDY are nearer to the voltage patterns VDD and VSS and the current pattern VC than to the read head signal patterns RDX and RDY, the effects are much more serious in a write mode than in a read mode.
Consequently, since the compensation values for RRO vary according to operating environment and the kind of the hard disk drive, the performance of the hard disk drive is affected by disturbances like NRRO and low frequencies of under 1 kHz which are not a servo control region of the FPC. NRRO means the rotation of the disk to form a distorted waveform without a specific period.
Referring to FIG. 3, a frequency response graph of the conventional FPC illustrates a current strength peak at around 340 Hz. The peak is generated by resonance between the characteristic frequency of the conventional FPC and the same frequency of noise. In this case, the vibration energy of the same frequency of the noise is strongly generated by resonance.
Thus, since a seek time and position error signal (PES) of the conventional hard disk drive are increased by the noise effect from the current pattern VC and the voltage patterns VDD and VSS, the difference between RRO compensation values, and the effect from low frequencies, the performance and yield rate of the conventional hard disk drive are deteriorated.
Accordingly, it is an object of the present invention to provide a hard disk drive having an improved flexible printed circuit (FPC) to minimize vibration energy at a specific frequency band generated in the FPC and to reduce the effects of noise on head signal patterns, thereby minimizing external effects on servo control.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing a hard disk drive having an actuator with a magnetic head to write and read information to and from a disk, a voice coil motor to drive the actuator, an FPC to transfer electric signals to the actuator and the voice coil motor, and a bracket to support the FPC, includes the FPC formed of head signal patterns, voltage patterns, a ground pattern, and a current pattern, wherein a hole is formed between the head signal patterns, and the voltage patterns, the ground pattern, and the current pattern.
In an aspect of the present invention, the starting point of non-contact between the FPC and the bracket, and the starting point of non-contact between the FPC and the actuator are arranged with the hole therebetween.
In another aspect, the hole is a slot aligned with the signal patterns or the holes are slots aligned with the signal patterns.
In yet another aspect, the edges of the slot are formed in a round shape.
According to the present invention, a hole is formed between the head signal patterns, and the voltage, ground, and current patterns in the FPC to reduce the effects of noise from voltage, ground, and current signals on head signals. In addition, vibration energy of about 340 Hz caused by the characteristic frequency of the FPC, and vibration energy applied from outside are reduced.